硫化态K－MoO_3／γ－Al_2O_3催化剂表面物种的XPS研究  

XPS Studies on Surface Species and Composition over Sulfided K-MoO_3/γ-Al_2O_3 Catalysts

作　　者：卞国柱[1] 伏义路[1] 方文秀[1] 

机构地区：[1]中国科学技术大学化学物理系,北京理化分析测试中心表面室

出　　处：《分子催化》1995年第5期329-338,共10页Journal of Molecular Catalysis(China)

基　　金：国家自然科学基金;北京中关村联合分析测试中心资助

摘　　要：采用Ｘ光光电子能谱（ＸＰＳ）及曲线拟合手段对硫化态Ｋ－ＭｏＯ_３／Ａｌ_２Ｏ_３合成醇催化剂进行了研究，分别考察负载量及硫化前不同条件预处理对催化剂表面的Ｓ、Ｍｏ组分的物种形式及各物种相对含量的影响，以及表面不同组分的相对组成。结果表明，根据其电子结合能变化，Ｓ组分可区分为ＳＯ_４￣（２－）、ＳＯ_３、Ｓ￣０、Ｓ_２￣（２－）、ＭｏＳ_２、ＭｏＳ_（２－ｘ）等六种存在形式不同的物种；Ｍｏ组分可区分为Ｍｏ￣（６＋）、Ｍｏ￣（５＋）、ＭｏＳ_（２＋ｘ）、ＭＯＳ_２、ＭＯＳ_（２－ｘ）等五种存在形式不同的物种。ＭｏＯ_３／Ａｌ_２Ｏ_３．重量比为０．０３的样品，Ｍｏ组分硫化还原不完全，表面Ｓ、Ｍｏ组分均以多种物种形式并存，ＭｏＯ_３／Ａｌ_２Ｏ_３比增加至０．０８和０．２４后，表面Ｓ、Ｍｏ组分中ＭＯＳ_２物种形式所占比例有所增加，样品的硫化还原也较彻底，但负载量增加至ＭｏＯ_３／Ａｌ_２Ｏ_３比为０．３５后，表面存在较多的Ｓ￣（６＋）物种和Ｍｏ￣（６＋）、Ｍｏ（５＋）物种，同时Ｋ组分在表面富集。对ＭｏＯ_３／Ａｌ_２Ｏ_３比为０．２４，样品硫化前不同条件预处理的研究表明，该样品与水蒸汽接触对其表面结构影响很大，与水蒸汽接触后再硫化，其表?Two series of sulfided K-MoO3/γ-Al2Os catalysts with different molybdenum loadings or with different pretreatments before sulfidation were prepared. The relative atomic concentrations on the surface of the catalysts were measured by means of X- ray photoelectron spectroscopy(XPS).The curve deconvolution of XPS spectra was utilized to examine the components of S、Mo spectra and the relative concentrations of these species. The results of curve deconvolution show that SO_4￣(2-), SO_3, S￣0, S_2￣(2-), MoS_2, MoS_(2-x) species in the S spectra and Mo￣(6+), Mo￣(5+), MoS_(2+x), MoS_2, MoS_(2-x)species in the Mo spectra exist on the surface of the samples. For the catalyst with a lower Mo loading [MoO3/Al2O3(weight ratio)=0.03], Mo species are only partly reduced and sulfided during sulfidation. The relative concentrations of the MoS_2, S￣(6+), S￣0,S_2￣(2-) components in the S spectra and the relative concentrations of the MoS_2, MoS_(2-x),Mo￣(6+), components in the Mo spectra show some differences as the Mo loading increases. With Mo loading incresed to MoO3/Al2O3=0.24, 80% of the Mo species are reduced and sulfided, MoS_2,S_2￣(2-) components in the S spectra and MoS_2, MoS_(2-x) species in the Mo spectra dominate. For the sample with MoO3/γ-Al2O3 weight ratio of 0.35 , about 40%of Mo species are not reduced and sulfided,and about half of the S species exists in S￣(6+) state.The experiments of different pre treatments before sulfidation show that as the oxidized sample comes in contact with water vapor, the structure of the sample is changes remarkably and the molybdenum components become difficult to be reduced and sulfided. The results of activity measurements indicate that the optimum Mo loadings is about MoO3/γ-Al2O3=0.24-0.35 for the synthesis of mixed alcohols from syngas; and the sulfided sample with its precursor contacted with water vapor shows a higher activity. The existence of some higher valence Mo species may be favorable to the synthesis of mixed alcohols.

关 键 词：硫化态 催化剂 XPS 钼基催化剂 三氧化二铝 

分 类 号：TQ426.94[化学工程]